Method of and apparatus for the deburring workpieces

ABSTRACT

Apparatus for the electrochemical deburring of metallic workpieces in which a fixture forms a support for the workpieces which, together with carbon particles and/or other abrasive particles, are agitated in an electrolyte.

United States Patent Inoue 1*May 13, 1975 METHOD OF AND APPARATUS FORTHE DEBURRING WORKPIECES [56] References Cited [76] Inventor: Kiyoshilnoue, 3 Chome, Kamiyoga. UNITED STATES PATENTS Tokyo, Japa 3.5218348/1970 Hewins .1 148/615 R l Nance: The porticn of the term of this3,533,928 10/1970 lnoue 204/213 X patent Subsequent to Oct 1988 3.620953ll/l97l lnoue 204/2l3 X h l as been disc aimed Primary Examiner-Ralph S.Kendall Flled? 1 Attorney, Agent, or Firm-Karl F. Ross; Herbert [21]App]. No: 168,173

US. Cl........ 204/129.46; l48/6.15 R; 204/213;

204/224 R Int. Cl 823p 1/04 Field of Search 148/615 R; 204/143, 2l3,

[57] ABSTRACT Apparatus for the electrochemical deburring of metallicworkpieces in which a fixture forms a support for the workpieces which,together with carbon particles and/or other abrasive particles, areagitated in an electrolyte.

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BY f arl ATTORNEY METHOD OF AND APPARATUS FOR THE DEBURRING WORKPIECESCROSS-REFERENCE TO COPENDING APPLICATION This application is acontinuation-in-part of copending application Ser. No. 714,252, filedMar. 19, I968, now US. Pat. No. 3,620,953 and a continuation-in-part ofcopending application Ser. No. 859,532, filed Apr. 21, 1969, now US.Pat. No. 3,533,928, which was in turn a continuation of application Ser.No. 598,391, filed Dec. 1, 1966, which application is now abandoned.

FIELD OF THE INVENTION My present invention relates to a method of andan apparatus for the deburring of metallic and other conductiveworkpieces whereby surface irregularities of such workpieces areeliminated.

BACKGROUND OF THE INVENTION Deburring apparatus of several types arecommonly in use in the metal-working field, primarily for the re movalof surface irregularities in cast, machined and molded metallicworkpieces. For the most part, such apparatus includes a tumbling drumprovided with agitating means for repeatedly casting the workpieces,generally in a liquid vehicle and sometimes in the presence of anabrasive, into contact with one another, against the walls of the vesselor drum or into contact with other bodies (e.g. of abrasive material)mixed with the Charge in the drum. This tumbling action mechanicallydislodges adherent materials while rounding off irregular portions andprojections integral with the metallic bodies. These systems, howeverare relatively slow and even defective when the deburring operation isto remove substantial amounts of material.

OBJECTS OF THE INVENTION It is, therefore, the principal object of thepresent invention to provide a method of deburring metal workpieceswhereby the rate of material removal and the surface finish of thetreated objects is significantly increased and improved.

Another object of this invention is to provide relatively simple andinexpensive apparatus for a high rate deburring of metallic workpieceswhile yielding a relatively high quality surface finish.

Yet another object of this invention is to provide a method of and anapparatus for the deburring of relatively large-dimension workpieces ofsuch nature that tumbling may be impractical.

SUMMARY OF THE INVENTION These objects and others which will becomeapparent hereinafter are attained, in accordance with the presentinvention, by a method of deburring metallic workpieces in which theliquid vehicle is agitated in contact with the workpiece to be deburredwhile mechanical contact between the surface of the latter and at leastsome other bodies is carried out concurrently with an electrochemicalmaterial-removal step.

As set forth in application Ser. No. 598,391, I have found,surprisingly, that electrochemical techniques hitherto used primarilyfor the electrochemical machining (ECM) and electrochemical grinding(ECG) of metallic bodies, wherein close tolerances are a necessity, canbe used effectively in conjunction with a tumbling or agitatingoperation to debur metallic workpieces or objects havingelectrolytically soluble surface portions. The surprising nature of thisdiscovery will become all the more apparent when it is recognized thatthe present method does not require a stationary electrode urged againstthe workpiece or juxtaposed therewith via a predetermined machining gap.

In accordance with the principal feature of this invention, anelectrochemical machining current. which may be direct or periodic(e.g., raw-rectified alternating current, pulsating direct current andordinary AC) is passed through the liquid vehicle which is constitutedas an electrolyte and may contain abrasive particles or merelyadditional bodies to facilitate mechanical deburring of the workpiecesconcurrently with the electrochemical action. While, in some cases, theworkpiece may be stationary and is connected with a pole of theelectrochemical machining sources, I have found that it is not necessaryto connect the workpiece directly thereto, and that the mere tumbling ofsuch workpieces in an electrolyte and in a drum having spacedapartcontact portions bridged by the electro lyte but not shortcircuited bythe drum itself. can effect electrochemical removal of material from theworkpiece surfaces.

While I do not wish to be bound by any theory in this regard and theprecise reasons why the current flow through the electrolyte iseffective to remove material from the surface of the conductiveworkpieces are not yet clear, it may be hypothesized that each of thework pieces acts as an electrode for the machining of others or asobjects undergoing electrolytic erosion against other conductive bodies.Since electrolytic oxydation of the workpiece at its surface isessentially nonreversible in the sense that agitation and mechanicalaction of the electrolyte carries away the oxide film as soon as it isformed and, even upon electrical (polarity) reversal, metal is notmaterially redeposited from the oxide onto the machine surface, theelectrolytic action is carried out as if a wire were directly connectedto each workpiece.

According to a more specific feature of this invention, the agitation ofa multiplicity of workpieces is effected in a tumbling drum which may beprovided at its base with one electrode portion and with a secondcontact or electrode, at a location spaced therefrom but in contact withthe electrolyte, the electrodes being connected across an AC or DCelectrochemicalmachining source (e.g. of the type described andillustrated in any of my applications Ser. No. 512,338 (US. Pat. No.3,475,312), Ser. No. 535,268 (US. Pat. No. 3,417,006), Ser. No. 562,857(US. Pat. No. 3,420,759), filed Dec. 8, 1965, .Ian. 19, 1966 and July 5,1966, respectively and copending application Ser. No. 714,252. Thetumbling drum can be upwardly open and rotatable about an axis tiltedupwardly at an angle of, say, 30 from the horizontal. In this case, theagitation is effected purely by rotation of the drum.

I have also found it to be possible, in conjunction with such a tumblingdrum, or when a stationary vessel is employed, to effect the agitationat least in part by magnetic means. Thus, if the workpieces treated inthe deburring operation or the other bodies involved are magneticallypermeable, I apply a magnetic field to them so as to effect theirdisplacement in the electrolyte; I also may distribute in the deburringvessel among the workpieces, particles or bodies of a magneticallypermeable material. Such bodies may be abrasive or electricallyconductive to facilitate electrochemical erosion of the workpieces orproduce the friction necessary for the deburring action. In fact, theparticles or bodies serving as the agitating means need not bemagnetically permeable under some circumstances, since the particles inthe electrolyte tend to respond to a rapidly changing magnetic field byrotating about the axis thereof. Thus, agitation may be promoted withthe aid of conductive as well as magnetically permeable particles.According to still another feature of this aspect of the invention, theparticles which are magnetically or electrically displaceable in theliquid vehicle, can be coated with abrasive material, incorporated in ormixed with abrasive particles which are not influenced by anelectromagnetic field.

Preference is given, in accordance with this invention. to pulsating oralternating electromagnetic fields for controlling the movement ofparticles and inducing electrochemical erosion of the workpiece surfacessince purely direct current has a tendency to produce agglomeration ofmagnetic particles in the deburring vessel.

According to another aspect of the basic invention, more fully describedin application Ser. No. 598,391, the agitation is carried out byrotating an electrode immersed in the electrolyte by, for example,rotating an electrode member in an irregular die cavity to deburr themachined surfaces thereof. Abrasive particles are here included in thedeburring vehicle while an electrolytic machining current is appliedbetween the workpiece and this rotating element. Inasmuch as this electrode member is not closely juxtaposed with the work piece surface andis rotated relatively rapidly, a more or less uniform surfacing iseffected. In accordance with this aspect of the invention, I prefer toincorporate in the vehicle a multiplicity of conductive particles whichhere act as intermediate electrodes and as they are dispersed by theagitation into the rotation of the die surfaces, each particle acts asan individual electrode to facilitate smoothing of the die surface. Theto tary electrode member imparts a centrifugal force to the abrasive andconductive particles contained within the electrolyte so that theseparticles are dynamically urged outwardly and forcefully brought intocontact or close juxtaposition with the surfaces to be treated toaugment the resulting mechanical deburring action.

According to yet another aspect of this invention, de burring is carriedout as augmented by a magnetic-field pressure which, when combined withthe dynamic flow or rapidly moving particles, with the centrifugal forceof tumbling or electrolyte displacement by a stirrer and withgravitational forces, magnetically urges the abrasive bodies against theworkpieces and the workpieces against one another. This magnetic-fieldpressure is, advantageously, supplied by electromagnetic means disposedexternally by the deburring vessel and is capable of applying inwardmagnetic forces to the magnetically permeable particles and workpieces.When the abrasive particles or auxiliary bodies serving to facilitatemechanical removal of irregularities and projections upon the workpiecesare magnetically permeable and/or the workpieces are of suchpermeability, a highfrequency magnetic field applied from without, inaccordance with this invention, induces an oscillation and/or amagnetostrictive expansion and contraction of the bodies so that thesimple tumbling action is accompanied by a magnetic vibration orpulsation of the body to improve the erosive operation. In thisconnection it can also be stated that the field may be of such naturethat vibration of the individual particles by the magnetic field iscoupled with a tumbling action of a rotary drum or a vibration thereofto increase the mechanical abrasion.

Another feature of this invention resides in the use of chemical actionin removing surface irregularities in combination with theelectrochemical and mechanical deburring action as described above. ThusI have found that surprisingly effective results can be obtained when achemical mordant or etchant for the workpiece material is incorporatedin the electrolyte. For as yet unknown reasons, the surface finish anddeburring rate obtained when, for example, ferric chloride is used asthe chemical etchant in the electrolyte, is better than that which wouldbe expected with either the etchant or the electrochemical action alone,while the rate of material removal exceeds the sum predictable from theindividual actions of the etchant and the electrochemical erosion.

According to a further feature of the present invention, theelectrochemical deburring of metallic workpieces is carried outconcurrently with agitation of the bodies in an electricallynonconductive tumbling drum rotatable about a recumbant axis (preferablyhorizontal or near horizontal) containing liquid electrolyte and theconductive (i.e., carbon) particles, together with the workpieces asdescribed therein. A pair of electrodes are in constant contact with theelectrolyte during rotation of the drum and are preferably disposed atremote ends of the electrolyte bath and are composed of a materialinsoluble in the electrolyte and free from electrolytic attack thereby.l have surprisingly found that excellent results can be attained whenthe conductive electrodes are constituted by the end walls of the drumand rotate therewith, the cylindrical drum wall forming the insulatingspacer for these electrodes. At least one but preferably both of theseend walls are provided with a passage for circulating the electrolytethrough the drum, the axial passage terminating in a fan-like array ofbores opening into the drum at the face of the end wall contacting theelectrolyte. The drum may further be provided, at least at regionsextending above the electrolyte level therein with apertures or ventsenabling evacuation of the gaseous products of the electrolyticdeburring of the workpieces,

Still another aspect of this invention resides in my discovery thatirregular deburring can be avoided by injecting an inert gas into theelectrolyte bath with the recirculating electrolyte stream. It appearsthat the inert gas creates labyrinthian paths for the electric currentflowing through the electrolyte, i.e., the ion mobility paths, therebydistributing the electrochemi cal action substantially uniformly. Thistechnique has the additional advantage that the inert gas upon evolutionfrom the electrolyte acts as a diluent for the nascent gases generatedby electrolysis and let off through the vents above the electrolytelevel. The inert gas may be admixed with the electrolyte in the bath orwith the liquid prior to its introduction into the tumbling drum.Furthermore, in accordance with the principles already discussed abovein general terms, I provide a magnetic flux radially through the drum,i.e., vertically when the drum is horizontal, preferably at a locationintermediate the electrode. to facilitate the agitation of the electrolyte, the workpieces, and the carbon particles forming intermediateelectrodes for the deburring action. These carbon particles have anabrasive or semiabrasive character so that they mechanically co-operatewith the workpieces to supplement the electrochemical deburring bymechanical erosion of the rough surfaces. Thus the carbon particles mayhe carbonaceous materials of relatively high hardness (e.g. syntheticdiamond as produced by the system described in my US. Pat. No. 3,207,582or the nondiamond but high-hardness carbon particles obtained whensynthetic diamond is made in accordance with that process).

As is apparent from the foregoing, and as described below in connectionwith FIG. 7, the method of removing burrs from the workpiece maycomprise the steps of attaching the workpiece to a conductive fixtureand connecting it to a source of electric current so that the workpieceis the anode in a direct current circuit, submerging the workpiece in atank containing conductive abrasive media immersed in a conductivesolution (i.e., an electrolytic solution), and simultaneously passing adirect electric current through said workpiece and the conductiveabrasive media and the conductive solution, and vibrating the tank forproviding random contact between the burrs and the conductive abrasivemedia. It will be apparent that it is inherent in the use ofelectrolytic solutions and the passage of current in the mannerdescribed that atomic oxygen is released on the burr surface to form anoxide coating thereon, whereupon the random contact wipes off theoxidized burrs.

Moreover, the source of electric current can be considered to be a fixedsource of electric potential, the conductive abrasive media to haveselected percentages of varying size particles providing a fixed rangeof electrical resistivity, the workpiece to be connected as an anodewhen oxygen is evolved, and the electric current in the circuit to beregulated by the amplitude and frequency at which the tank is vibrated.

DESCRIPTION OF THE DRAWING The above and other objects, features andadvantages of the present invention will become more readily apparentfrom the following description, reference being made to the accompanyingdrawing in which:

FIG. 1 is an axial cross-sectional view through a tumbling drum of adeburring apparatus in accordance with this invention;

FIG. 2A is an axial cross-sectional view of an electrode forming an endwall of the drum;

FIG. 2B is an elevational view thereof;

FIG. 3A is a cross-sectional view through a modified electrode;

FIG. 3B is an elevational view of this latter electrode;

FIG. 4 is a diagram of the electrochemical deburring system of thepresent invention;

FIG. Sis a view similar to FIG. 1 of a modified system for deburringmetallic workpieces;

FIG. 6 is an axial cross-sectional view through a tumbling systemembodying other principles of this invention;

FIG. 7 is a diagram ofa continuous deburring apparatus in accordancewith the principles of this invention;

FIG. 8 is an axial cross-sectional view through a deburring apparatususing a stationary system and diagrammatically showing theelectrolyte-circulating means therefor; and

FIG. 9 is a cross-sectional view along the line IX IX of FIG. 8.

SPECIFIC DESCRIPTION AND EXAMPLES In FIG. I, I show a rotary tumblingsystem for the deburring of metallic workpieces in which a closed drum1010 has a pair of end walls 1017 and 1018 forming electrodes andretaining the electrolyte 1011 in the drum. Between the conductiveelectrodes 1017 and 1018, the drum is formed as a nonconductive sleeveI041 composed of or lined with electrically insulating material such asa hard rubber or an electrolyteresistant synthetic resin (e.g. apolyacrylate). Electrically insulating rubber gaskets 1042 are providedbetween the drum body 1041 and the electrodes 1017 and 1018. The drummay also be formed with a door 1045 to permit the workpieces andintermediate electrodes to be introduced into the interior of the drum.

The electrodes 1017 and 1018, which are inert to the electrochemicalaction and to the electrolyte, are com posed of graphite or an insolublemetal (e.g. stainless steel or monel). The drum 1010 is mounted upon apair of trunnions 1024a and 102411 extending upwardly from a base 1026and defining for the drum a horizon tal axis. The drum is, in turn,carried by a pair of tubular shafts 1023a and 10231) affixed to therespective electrode end walls 1017 and 1018 as described in connectionwith FIGS. 2A, 2B and FIGS. 3A, 3B.

The drive means for the drum comprises a motor 1027 whose output shaft1028 is connected by a V-belt transmission 1030 with the hollow shaft10230 to rotate the drum about its horizontal axis. The electric currentfor the electrochemical deburring operation is pro vided by a powersupply 1019 and is applied via a pair ofbrushes 1019a and 1019b to theelectrodes 1017 and 1018 via their shafts 1023a and 1023b. Electrolyteis circulated through the drum by a pump 1039 and a circulating systemincluding an inlet pipe 1040 connected with the tubular shaft 1023b. Thetubular shaft 1023a leads electrolyte from the drum to a return tube1043 ending at a surface 1044.

The electrodes 1017 and 1018 may be provided with a fanshaped array ofbores (FIGS. 2A and 2B) or a central array of mutually parallel bores(FIGS. 3A and 38), while means may be provided for injecting a gas intothe liquid-circulating stream (FIG. 5) and a magnetic field may beapplied in the radial direction (FIGS. 5 and 6). In the embodimentillustrated in FIG. 1, however, the end walls and electrodes 1017 and1018 are provided with axially extending bores 1017' and 1018'communicating with the hollow shafts 1023a and 1023b, respectively.

Within the drum, as described in my application Ser. No. 598,391,copending with application Ser. No. 714,252, I provide, in addition tothe electrolyte 1011, a mass of metallic workpieces 1012 (shown asrectangles) accompanied by conductive particles 1013 (hatched circles)and if desired magnetic and abrasive particles as described inapplication Ser. No. 598,391. The electrolyte may be any of theelectrochemical machining solutions described in applications Ser. Nos.512,338, 535,268 and 562,857, all having been mentioned earlier andhaving been copending with application Ser. No. 714,252. The particles1013 are composed of carbon and act as intermediate electrodes.

An important aspect of this invention resides in the fact that thecarbon particles are formed of relatively high-hardness carbonaceousmaterial capable of withstanding metallic abrasion in the tumbling ofthe workpieces. Suitable particles may be made by sintering py' rolyticcarbon or by the electric-discharge technique set forth in my US. Pat.No. 3,207,582. In addition, the carbon particles may contain siliconcarbide or the like abrasive powder dispersed therein prior tosinteringv As a result, the electrochemical action is augmented by amechanical smoothing of the workpieces concurrent with electrochemicalremoval of projecting portions of the workpieces (i.e. burrs). Thedeburring power supply 1019 may be any electrolysis source as describedin application Ser. No. 598,391 and the other applications mentionedearlier. Suitable sources may be alternating current, pulsating directcurrent or filtered direct current as there described.

EXAMPLE I Using the system of FIG. 1, deburring was carried out in aI592 sodium chloride solution upon a mass of 35% by volume of steelworkpieces having a diameter of 10 mm and a length of mm. Conductiveparticles, i.e., sintered pyrolytic graphite and silicon carbideparticles with a diameter of about 5 mm were used in a ratio to theworkpiece quantity of about 1.15:1; it was possible to increase thedeburring rate over conventional systems using only aluminum oxideabrasive particles and a similar drum (diameter 300 mm, axial length of7 mm, electrolyte quantity 5 liters, current 80 amp), in terms of thequantity of material removed per unit time, from to 30 times and theyield improved surface finish.

In FIGS. 2A and 28, I show a modified version of the terminal electrodefor the drum of FIGS. 1, 5 and 6, the electrodes l l 17 generallycomprising a disk 1117a of graphite or other electrochemically inertmaterial attached at a flange lll7b to the tubular shaft 1123. A fanlikearray of bores l l 17c is formed in the disk 1117a and open at the innerface 1ll7d in contact with the electrolyte within the drumv From FIG. 28it is apparent that the bores are distributed in conical arrays aboutaxis of rotation of the drum (represented at 1125) so that a number ofthese bores open into the drum above the liquid level (see FIG. 1) ateach of the electrodes 1017 and 1018. Thus gas forming above theelectrolyte path can pass through the uppermost bores and can beentrained with the liquid stream leaving the drum and flowing to thereservoir 1044. In this reservoir, which is open to the atmosphere, thegases entrained in the liquid can evolve into the atmosphere. Thefanlike array of bores has the additional advantage that, at the inletelectrode (e.g. electrode 1018), the bores disperse the liquid and anygases entrained therein (FIGS. 5 and 6) to insure fine distribution ofgas bubbles in the electrolyte bath and even deliver some gas above theelectrolyte to act as a diluent for the electrolytically evolved gases.The bores 1117c converge axially away from the drum to communicate withthe tubular shaft 1123 and thus form a manifold.

Electrode 1217 of FIGS. 3A and 38 represents a modified construction inwhich the disk 1217a is formed with a plurality of mutually spacedparallel bores 1217c which are located in the region of the cen ter ofthe disk and communicating with the hollow shaft 1223 which is attachedto the disk 1217a at a flange 1217b. This embodiment has the dispersingadvantages mentioned in connection with the electrodes of FIGS. 2A and2B but does not evacuate gases from above the electrolyte level aseffectively. Eiether of the electrodes of FIGS. 2A and 2B and of FIGS.3A and 33 can be used in the drum deburring systems of FIGS. 1, 5 and 6.

In FIG. 4, there is shown a diagram of the principles of the presentinvention as discussed in greater detail in application Ser. No.598,391. In this FIGURE, I show the workpieces 1012 as fortuitouslylocated between a pair of carbon particles 1013 and the electrodes 1017and 1018. If electrode 1017 is positive as shown for the purposes of theexplanation of this electrochemical phenomenon, it will be seen that aproximal carbon particle 1013 received an inducted charge so that itsregion juxtaposed with surface 1012 in the electrolyte 1011 acts as anelectrode to sustain electrochemical machining of this workpiecesurface. The random distribution of conductive particles and workpiecesbetween the electrodes is effective to insure practically uniformelectrochemical treatment of all workpiece surfaces.

However, burrs or other projections invariably lie at a shorter distancefrom one of the terminal electrodes or an effective intermediateelectrode than the other portions of the surface from which theyproject. The electrochemical machining current density is substantiallyhigher at these protuberances and machining preferably occurs in theseregions. Any mechanical smoothing is cumulative to the electrochemicalaction. It will be appreciated also that the presence of gas bubbles inthe electrolyte augments the machining action and its specific attackupon protuberances and the burrs. It has been found that the gas bubblestend to adhere to the surface of the workpiece in regions between theburrs and effectively insulate these regions while increasing thecurrent density at the burrs. This too improves the surface fmish andcan be controlled by injecting inert gases into the system as will bedescribed in connection with FIG. 5. The term inert, however, must beconstrued in terms of the activity performed here. When the evolvedgases include hydrogen, it will not be advisable to add oxygen and viceversa. Even normally active gases may be considered inert if they arenonexplosive when used in the presence of gases evolved from thedeburring bath.

In FIG. 5, there is shown a horizontal drum 1310 with a central body1341 held between a pair of gaskets 1342 and electrodes 1317 and 1318 ofthe type shown in FIGS. 2A and 2B. The electrodes are carried betweenthe tubular shafts 1323a and 1323b whose slip rings are in contact withbrushes 1319b and 1319a of the electrochemical machining power supply1319. A motor 1327 drives the drum about its horizontal axis whileelectrolyte is circulated through the drum via a pump 1339 from thereservoir 1344 and a line 1340 communicating with hollow shaft 1323b.The electrolyte from the drum is returned via line 1343' to thereservoir.

In accordance with the principles of the present invention, gas isinjected into the electrolyte prior to its passage into the drum, thegas-supply source being shown at 1350 in FIG. 5. The source is a tank ofair, argon, carbon dioxide, nitrogen or the like which is connected viaa valve 1350a and a line 13501) with the hollow shaft 1323b of electrode1318. When the gas is forced under high pressure into the electrolytewhich, in turn, is under pressure of pump 1339, the liquid/gas mixtureentering the drum through the electrode I318 expands to evolve the gasin the form of bubbles and, in part, to induce some of the gas into thedrum above the electrolyte, thereby diluting the nascent gases releasedby electrolysis. The gas bubbles within the electrolyte adhere to theworkpiece surfaces and augment the deburring action. An electromagnet1315, whose flux can be represented by arrow I is provided beneath thedrum 1310 and is effective to increase the electrochemical machiningaction.

As described in application Ser. No. 598,391, the magnetic field may beof unidirectional or alternating type while the magnet itself may bestationary or reciprocating. The magnet may be energized by a highfrequency a.c. source in addition to a low-frequency vibrating oroscillating source. The high-frequency source preferably operates at 400kHz to 50 kHz and ends above sonic frequencies while the low-frequencysource operates at, say, 30 to 40 Hz. It appears that the magnetic fieldhas a two-fold action whereby it induces a dynamic flow of liquidelectrolyte and secondly, imparts magnetically attractive or repulsivemotions to the workpieces when they are permeable.

In the system of FIG. 6, the drum 1410 has a cylindrical body 1441 whichis preferred to evolve gases and permit electrolyte to enter the drum asthe latter is rotated in a bath 1435. A hood 1451 overlies the bath 1435and collects the evolved gases. Here too, the tumbling drum 1410 has apair of disk-shaped electrodes 1417 and 1418 which are insulated fromeach one another by the gaskets 1442 although the electrodes are herenot perforated. Nontubular shaft 1423a and 1423b rotatably support thedrum 1410 into a pair of trunnions 1424a and 1424b. The drive means isconstituted by a motor 1427 and a V-belt transmission 1430 connectingthis motor with shaft 1423a. An electrolysis power supply 1419 applieselectric current to the electrodes 1417 and 1418 by the brushes 1419aand 1419b. A magnetic field is applied, as previously described, by thecoil 1415 in the vessel 1435.

FIG. 7 shows a continuous system for the deburring of metallicworkpieces wherein a succession of workpieces is deposited from a hopper1552 upon a belt 1553 which directs these workpieces to a perforatedendless belt 1510 which functions similarly to the drum of the precedingembodiments. The endless belt 1510, which has horizontal stretch 1510areceiving the workpieces 1512 from the conveyor 1553, passes over anidler pulley 1510b into the electrolyte bath 1511 in a vessel 1535 offunnel-shaped construction prior to emerging from the bath over afurther pulley 1510c. Within, the vessel 1535, I provide agitating meansin the forming electromagnet 1537 which vertically displaces an armature1530 against a pair of compression springs 1538a to jumble the workpieceand carbon particles contained on the stretch 1510d of the belt passingthrough the electrolyte bath. The armature 1538 carries a number ofrollers 1538b which supports the belt in this region withoutfrictionally impeding its movement.

Upon leaving the electrolyte bath 1511, the conveyor 1510 has ahorizontal stretch 1510c overhanging a collecting receptacle 1554 inwhich the deburring workpieces are caught, the band being then returnedto the horizontal stretch 1510a by downward stretch 1510f, a

horizontal stretch l5l0g and a vertical stretch 1510/1.

Intermediate electrodes are formed by a mass of carbon particles 1513 aspreviously described. The carbon particles are retained in a supplytrough 1555 and are carried by a bucket conveyor 1556 to the vessel 1511where they are deposited upon the mass of workpieces entering the bath.The band 1510 is, as previously indicated, perforated and has openingsthrough which the carbon particles may pass as they settle from theelectrolysis zone. Thus carbon particles which settle through the belt1510 are discharged at an outlet 1543 of the vessel and are collectedupon a sieve conveyor 1557 which carries them to the trough 1555. Theelectrolyte passing through the sieve conveyor 1557 is collected in thereservoir 1544 and recirculated by a pump 1539 and a line 1540 to thebath 1511.

The electrodes may, as described in application Ser. No. 598,39l,comprise vertical rods 1518a, 1518b and 1518c which can be angularlyoscillated about respective vertical axes and vertically reciprocated bythe mechanism shown for similar electrodes in the lastmentionedapplication. I have found, moreover, that improved power utilization canbe obtained when a polyphase power supply is available and the number ofelectrodes is equal n X P where P is the number of phases (usuallythree) available as the supply and n is an integer. In this system, eachphase is applied between one pair of electrodes or the correspondingelectrodes of a pair of sets, each set having n electrodes. In thesimplified system of FIG. 7, the power supply comprises a three-phasesource 15190 which supplied a conventional Y or A transformerdiagrammatically represented at 151% each of the output faces of whichis applied across a pair of the electrodes 15180 through 1518c. Theconnections to these electrodes are shown both for Y and A systemsalthough it will be understood that only one of these systems may be inuse at any time. In the Y system, the neutral pole may be grounded atthe transformer. This arrangement permits each phase ofa three-phasecurrent to be effective and provides a greater effectiveness of thesupply power without the expense rectifier systems which would benecessary to produce direct current and the complex circuitry whichwould be necessary to convert the three-phase force current tosingle'phase balanced current is operating the deburring device. It hasbeen found that the system is particularly desirable when a large numberof workpieces with a relatively large total volume is to be deburred atone time.

In FIGS. 8 and 9, I show another embodiment of the present invention inwhich no continuously displaceable endless surface is provided and theagitation of the electrolyte, carbon particles and workpieces, iscarried out by means of pulsed jets or high-velocity streams ofelectrolyte directed tangentially into the vessel at the deburringregion. This system, while affording some mechanical smoothing bycontact of the workpieces with the carbon particles and the electrodesand wall of the vessel, primarily is effective to promoteelectrochemical removal of material from the workpiece surfaces withoutany movable apparatus members. The freedom of this system fromvibrational and rotational movement of the electrodes, containers andthe like eliminates the need for drive motors journaling assemblies andthe like, thereby making the entire apparatus more practical and lessexpensive, especially where small quantities of workpieces are to betreated.

In accordance with the principles of the present invention, theapparatus comprises a stationary vessel 1610 of electrically insulatingmaterial having an upwardly open potshaped chamber 1643 with anarcuately concave bottom 1643a. A pair of electrodes 1617 and 1618disposed at diametrically opposite locations along the inner wall of thechamber and energized by an electrochemical machining deburring powcrsupply 1619 of the character previously described. The vessel containsan electrolyte 1611 in which the workpieces 1612 (diagrammatically shownas circles) are distributed. The carbon particles 1613 are composed ofsintered carbon to which abrasive powder has been added and may be usedin conjunction with abrasive particles which contain no conductivematerials, When a number of pairs of electrodes are provided in thissystem, the considerations discussed in connection with FIG. 7 apply andthe power supply may include a polyphasecurrent source each phase ofwhich is connected across a respective pair of electrodes or arespective pair of electrode sets.

In the present embodiment, the agitation of the electrolyte, workpiecesand carbon particles is carried out by a fluid stream and the bottom1643a of the vessel may thus be provided with a plurality of liquidinlets 1623a. 1623b 1623c, l623n forming electrolyte jets orientedgenerally tangentially to an imaginary circle C centered upon thevertical axis of the chamber and tangential as well to the curvature ofthe floor of the vessel as will be apparent from FIGS. 8 and 9. Theseinlets individually extend through the vessel 1610 and communicate vialines 1640a... etc. with a pump 1639 drawing electrolyte from thereservoir 1644. Electrolyte is returned to the reservoir via a line1643'. Each of these lines is provided with a respectiveelectromagnetically operable valve 1659a, etc. which successively pulsethe electrolyte jets introduced into the vessel. Consequently, a vortexagitation ofthe electrolyte is provided which dynamically coacts withgravitational force to produce the desired turbulence. When moreturbulence is desired, the jets can be pulsed in random sequence ratherthan in succession as indicated. The deburring electrolyte may beadmixed with inert gas (see FIG. from a cylinder 1650 and a valve 16500which may be injected into the electrolyte stream or may be addedexclusively through one of the inlet passages (ie, passage 16230 in thesystem of FIGS. 8 and 9).

EXAMPLE I] A series of comparative tests were carried out with thestationary vessel arrangements of H65. 8 and 9, with a rotary vesselsystem with a vibratory vessel system as described below. Theelectrolyte was an aque ous solution of by weight of potassium nitriteand the workpieces were hexagonal nuts composed of iron and of 8 mmdiameter. The nuts were of first grade .llS standard, black. class 4M8SS4lB-D with a total volume of 500cc. The deburring elements added tothe system were carbon particles of l5 mm diameter or abrasive particlesof alumnia or silica, each of IS mm diameter. When particles were added,a total quantity of 2,000 cc of such particles were used. The rotarysystem involved 55 drum revolutions per minute, the vibratory systemapplied drum-vibrations of 1,500 cycles per minute and the jet systemmade use ofa electrolyte pressure of 5 and 15 kg per cm Four jets wereemployed in each case and the following Tables give the total quantityof material removed in the deburring process, the voltage and amperageprovided for the electrochemical action and the particle wear inpercents by weight. The deburring operation for each case was carriedout equally for 10 minutes.

Particle wear Deburred Particles Voltage Amper- (72 by weight) quantity8 (grams) l. Rotary System (a) Carbon only 37 88 3 48 (b) Carbon 50vol.'/( 72 35 4 N 0,, 50 vol.% (C) Al Ct 50 V0l. 7r 90 0| 20 SK); 50Vol.7;

2. Vibratory System (a) Carbon only 30 80 5 42 (b) Carbon 50 Vol.9? 65 625 M 0 50 Vol.7? (c) [M 0 S0 volfil B5 40 0] 22 SiO 5O VOl.%

3. Jet System with S kg/cm electrolyte pressure (a) Carbon only 18 90 452 (b) Carbon 50 vol/Z Al O 50 vol.7 60 3.6 38 (0) M 0, vol?! 62 45 0.226 SiO 50 volf/i 4. Jet System with 15 kg/cm electrolyte pressure (a)Carbon only l5 l0() 3 56 (b) Carbon 50 vol/7r N 0 50 volfir 43 62 4 39(c) M 0 S0 vol.7r

in addition, an electromagnet 1615 may be provided below the vessel asshown in FIG. 8 to augment the dynamic movement produced by the liquidjets by electromagnetically induced movements. it will also beunderstood that various combinations of the several systems may beprovided as well. Thus, the systems of FIGS. 1, and 6 may provide pulsedelectrolyte jets to increase agitation while similar jets may beprovided in the system of FIG. 7. A conveyor belt may be passed throughthe vessel of FIG. 8. The vessel of H6. 8 may also be vibrated byelectromagnetic means as shown in FIG. 7 or may co-operate withangularly oscillatable and vertically reciprocable electrodes as thereshown.

I claim:

1. The method of removing burrs from a workpiece, comprising the stepsof:

supporting said workpiece in conducting relationship with a source ofelectric current. said workpiece being the anode in a direct currentcircuit;

submcrging said workpiece in a tank containing conductive abrasive mediaimmersed in a conductive solution, said solution being an electrolytesolution; and simultaneously passing a direct electric current throughsaid workpiece and said conductive abrasive media and conductivesolution, to release atomic oxygen on the burr surface and to form anoxide coating on the surface of the burrs, and

vibrating said workpiece relative to said solution and said abrasiveconductive media for providing ran dom contact between said burrs andsaid conductive abrasive media to wipe off said burrs.

1. THE METHOD FOR REMOVING BURNS FROM A WORKPIECE, COMPRISING THE STEPSOF: SUPPORTING SAID WORKPIECE IN CONDUCTING RELATIONSHIP WITH A SOURCEOF ELECTRIC CURRENT, SAID WORKPIECE BEING THE ANODE IN A DIRECT CURRENTCIRCUIT, SUBMERGING SAID WORKPIECE IN A TANK CONTAINING CONDUCTIVEABRASIVE MEDIA IMMERSED IN A CONDUCTIVE ABRASIVE MD2EDIA AND CO SOLUTIONBEING AN ELECTROLYTE SOLUTION, AND SIMULTANEOUSLY PASSING A DIRCTELECTRIC CURRENT THROUGH SAID WORKPIECE AND SAID CONDUCTIVE ABRASIVEMEDIA AND CONDUCTIVE SOLUTION, TO RELEASE ATOMIC OXYGEN ON THE BURRSURFACE AND TO FORM AND OXIDE COATING ON THE SURFACE OF THE BURNS, ANDVIBRATING SAID WORKPIECE RELATIVE TO SAID SOLUTION AND SAID ABRASIVECONDUCTIVE MEDIA FOR PROVIDING RANDOM CONTACT BETWEEN SAID BURNS ANDSAID CONDUCTIVE ABRASIVE MEDIA TO WIPE OFF SAID BURRS.